Method of manufacturing arsenate of lead.



45 3 sented by the following equation To all ichom it may concern: ,"Be'it known that I, EDWIN o. sassrow, or MIDLAND,

enwm

MICHIGAN, riSSIGNOE '10 THESDOW CHEMICAL COMPANY, OF MIDLAND, MICHIGAN, A COBPOBATION OF MICHIGAN.

METHOD OF IdiA lN'UFAC-TURING ABSENA'IE F LEAD.

1,014,742. 30 Drawing.

Specification of Letters Eatent.

, Patented Jan. 16,1912.

0. Bans'row,

a citizen ofthe United States, and a resident of Midland, county of'Midland, and

tinguish it from other inventions.

" "EState .of Michigan,

have invented a new and useful Improvement in Methods of ii -,,Mauufacturing Arsenate of Lead, of which fthelfollowing is. a specification, the principle ofthe invention being herein explained and the best mode in which I have contemplated applying that principle, so as to dis- The improved method, or process, of man-- ufacturing lead arsenate in hand, involves the precipitation of a soluble arsenate solution,.as for example, sodium arsenate solution, by means of solid lead chlorid.

The several steps involved in carrying out the present process will be hereinafter fully claims.

described and particularly pointed outin the I The. following description sets forth in i detail an approved mode of carrying out the invention, such disclosed mode, however, constituting but one of the several ways in which the principle of the inven- .tion may be used.

In accordance with the present methodof I procedure, the solid lead chlorid, obtained It has been found that by stirring such mixact upon the soluble arsenate to. form the from any convenient source, is mixed in with a solution-0f a suitable arsenate, but in the presence of water insufiicient in amount to dissolve the lead chlorid. Such chlorid is preferably utilized in finely divided form. rather than in the coarsely crystalline form.

ture for a longer time than necessary where solutions are used, the lead chlorid will reinsoluble lead arsenate. The exact composition of the precipitate obtained by such reaction is dependent upon the ratio of base to arsenate in the arsenate solution. When' sufficient base is present, normal lead arsenate Pb,(AsO is obtained as reprewhile if lessof such base is presentfa lead arsenate lugher 1n arsenlc is produced; One reactlon, which occurs when notg'enough' 1; base is present to produce a normal arsenate, is represented by the following equation ess,

Application and June 10, 1911. serial a... 882,446.

mercial sodium arsenate, which is a convenient soluble arsenate for usein this procis usually a mixture of arsenates, containing both acid arsenates Na,HAsO, and NaH AsO If the normal lead arsenate is desired, a certain amount of a suitable alkali, such as'soda ash Na,CO,, should be added, the proper amount of such alkali" being such as will be the equivalent of the hydrogenv in the arsenate, or mixture of acid arseuates above referred to. This soda ash does not necessarily go immediately into combination with the acid arsenate, since the disodium. arsenate will not react. The efiect, however, after the lead chlorid has be'en-added,-is the same as though both acid arsenates had been at once converted into the normal arsenate.

It might appear at first sight that the re action between the soild lead chlorid and soluble arsenate could not be carried to completion, because, the resulting product being soild, all of the lead chlorid would not be reacted upon, but particles of it would be inclosed in an impervious coating of the lead arscnate. This tendency, however, it has been discovered can be successfully overcome by subjecting the mixture to prolonged stirring or agitation. This operation can be satisfactorily conducted in a wooden tank provided with a suitable stirrer and with the solution so'concentrated that the resulting mass has the consistency of a thick cream.

Afterthe conversion of the lead chlorid into the arsenate is complete, the charge is run to a filter, or filter press, and the" excess of water-thereby removed, the arsenate being left in a paste ofthe desired consistency If desired, of,

to meet the requirements. course, the mixture constituting the charge may separation step.

' Other modes 'of applying the 1 9 my invention may be employed instea be allowed to settlepreliminarily'tothls the'one explained, change being'made'a -H gardsthe process herein disclosed, the step. or steps statedby any. one of the}.

following claims or the equivalent such statedste or steps be employed. g I there ore particularly point out and dis-, I

tinctly claim as my invention 1. In a method of making lead arsenate, the. step which consists inmixing solid lead chlorid with'soluble arsenate in the presence of water insutficient to dissolve said chlorid. 2. Inv a method of making leadarsenate,

the step which consists in mixing lead chlorid with sodium ai'senate in the presence of water: insufiicient to dissolve said chlorid.

3. In a method of niaking'lead arsenate, the step which consists in mixing lead LlllOlld with. acid sodium arsenate in the presence of water insuflicient to dissolve said chlorid.

at. The method of making lead arsenate, which consists in mixing solid lead chlorid in finely divided form With a solution of a soluble arson-ate, the quantity of Water pres ent being insuflicient to dissolve said chlorid;

subjecting the mixture to prolonged stirring, whereby lead arsenate is formed; and then separating such arsenate from the solution.

5. The method of making lead arsenate, which consists in mixing solid lead chlorid in finely divided form with a solution. of

sodium arsenate, the quantity of Water pres ent being insufiicient to dissolve said chlorid; subjecting the mixture to prolonged stirring, whereby lead ai'senate is formed; and then separating such ai'senate from the solution.

6. The method of making lead arsenate, which consists in mixing solid lead chlorid in finely divided form with a solution of acid sodium ai 'senate, the quantity of water present being insutficient to dissolve said chlorid; subjecting the mixture to prolonged stirring, whereby lead arsenate is formed; and then separating such arsenate from the solution.

Signed by meithis 6th day of June 1911.

' EDWIN O. BARSTOW.

Attested bj I G. LEE/CAMP, D. NEWLAND. 

